1. Field of the Invention
The present invention relates to a liquid crystal display for a vehicle and, particularly, to a liquid crystal display which adjusts liquid crystal drive voltage based on the temperature of a liquid crystal display panel so that the contrast of the liquid crystal display panel becomes optimum.
2. Description of Background Art
In a liquid crystal display, the contrast of a liquid crystal display panel changes according to an ambient temperature environment even if liquid crystal drive voltage remains the same. Then, Japanese Laid-Open Patent Application No. 10-31204 proposes a liquid crystal display which automatically adjusts liquid crystal drive voltage based on the temperature of the liquid crystal panel detected by a temperature sensor such as a thermistor.
In other words, the contrast of the liquid crystal display is correlated with its temperature. In order for the liquid crystals keep a high contrast between the time when liquid crystals are on in a transparent state, and the time when the liquid crystals are off in a non-transparent state, the drive voltage must be reduced as the temperature of the liquid crystals becomes higher. Therefore, in the above prior art, the ambient temperature of the liquid crystals is detected by a temperature sensor, and a temperature compensation circuit is provided to increase drive voltage when the ambient temperature drops. Likewise, this temperature compensation circuit reduces drive voltage when the ambient temperature rises.
In the above prior art, the temperature of a liquid crystal display panel is represented by the detection temperature of a temperature sensor for detecting the inside temperature of a housing. However, in a liquid crystal display which is often exposed to direct rays of the sun as when it is employed as the meter panel of a motorcycle, a temperature difference occurs between the ambient temperature of the inside of the housing and the actual temperature of the liquid crystal display panel. This makes it difficult to apply the optimum liquid crystal drive voltage. To solve this technical problem, a technology for mounting a temperature sensor to a liquid crystal display panel is also proposed.
However, when the temperature sensor is mounted to the liquid crystal display panel, an electrode for connecting this temperature sensor to a circuit board are newly required, thereby causing technical problems such as an increase in the number of parts or a complicated production process.